A load cell is a transducer that is used to convert a force into an electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a strain gauge. The strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A load cell usually includes four strain gauges in a Wheatstone bridge configuration. Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available. The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used. The output of the transducer can be scaled to calculate the force applied to the transducer. The various types of load cells that exist include Hydraulic load cells, Pneumatic load cells and Strain gauge load cells.
Strain gauge load cells are the most common in industry. These load cells are particularly stiff, have very good resonance values, and tend to have long life cycles in application. Strain gauge load cells work on the principle that the strain gauge (a planar resistor) deforms/stretches/contracts when the material of the load cells deforms appropriately. These values are extremely small and are relational to the stress and/or strain that the material load cell is undergoing at the time. The change in resistance of the strain gauge provides an electrical value change that is calibrated to the load placed on the load cell. Typically, strain gauges are formed from resistors in a Wheatstone bridge configuration. A Wheatstone bridge is an electrical circuit used to measure and unknown resistance by balancing two legs of a bridge circuit. One leg of which contains the unknown value. Wheatstone bridges are made up of four resistors or loads in a square with a voltage meter bridging two corners of the square and power/ground connected to the other corners. In the case of a load cell, these resistors are strain gauges.
The present invention relates to a load cell that transmits and measures linear forces along and moments about up to three orthogonal axes. More particularly, a compact load cell body is disclosed for maximizing the rigidity ratio of the load cell body to the load cell sensing region.